Best temp and time to cook Hamburger Helper rice?

I can cook any rice real well, but when it comes to those par boiled, all-in-one, pan-cooked meals with rice I cannot seem to cook it within the requested time frame. Last night it was suppose to simmer 25 minutes. It took me an hour to get the rice somewhat edible, still. With those meals what do they mean when it asks to "bring to a boil and stir occasionally. Then turn down the heat and simmer for 25 minutes"? How much do I put the heat on to simmer rice? Low? Med-Low? Med? Med High? Help! I feel stupid for screwing up Helper meals! lol....